Various solid materials are known to contain hydrocarbons and the recovery of such hydrocarbons from such solids has attracted significant interest, particularly in recent years. Examples of such solid materials are oil shale, tar sands, coal and lignite. Various methods have already been proposed in the art to recover the organic materials from such solids. One such method that has been proposed is the so-called supercritical extraction, which allows recovery of a significant amount of the organic material contained in such solids. Supercritical extraction has been disclosed in particular for the recovery of organic materials from oil shale. Recovering a significant amount of the organic material of such solids as oil shale is a continuing goal in the industry.